The invention relates to the separation of the heavy components of a blood sample (called the heavy phase), i.e., white cells, red cells and platelets from the lighter components (called the light phase), i.e., serum and plasma of blood.
Such separation is typically performed by centrifuging the blood sample so that the heavier components are forced to one end of a container and the lighter components separate to the other.
After the separation, the two phases can be physically separated into isolated containers and tested individually. If this physical separation is not made or is not readily made, the separate phases of the blood sample will become contaminated, for example, as the red blood cells begin to liberate potassium. This and other contaminants could interfere with the blood sample testing.
The physical separation of the two phases of the blood sample can be achieved during the initial centrifuging step of phase separation or shortly thereafter through the use of a mechanical separator, of which there are many. U.S. Pat. Nos. 4,492,634, 3,508,653, 4,230,584, 3,960,727, 3,972,812, 3,945,928, 4,202,769, and 4,001,122 all disclose apparatus which physically separate the two specific gravity differentiated phases of a blood sample during or shortly after the centrifuging process.
Such blood separation apparatus usually includes a container similar in shape to a test tube, and an insertable barrier plate usually housing a one-way valve and filter material and providing an effective seal along the inside wall of the container. This barrier plate can be made to have a certain specific gravity which is greater than the light phase of the blood such that during the centrifuge phase separation, the barrier plate will move through the lighter phase until it reaches a level corresponding to its specific gravity. The barrier plate can also be manually inserted past the light phase to the phase barrier, after centrifuging. This barrier plate, once in place, defines two isolated chambers in the main container, one for each phase.